Rotary compressor

ABSTRACT

A refrigerant being low in both ODP and GWP and containing at least hydrofluoroolefin having a double bond of carbon is used. By providing a first compression-chamber oil feed path for feeding refrigerating machine oil to a compression chamber  15  after the refrigerant has been enclosed therein, effects on the global environment can be suppressed and moreover temperature increases of the refrigerant due to re-expansion heating and feeding of high-temperature refrigerating machine oil can be suppressed, i.e., decomposition of the refrigerant can be inhibited.

TECHNICAL FIELD

The present invention relates to a rotary compressor which uses a refrigerant containing no chlorine atoms, being low in GWP (Global Warming Potential) and containing at least hydrofluoroolefin having a double bond of carbon, and which is to be incorporated into refrigerating cycle apparatuses for room air conditioners, automotive air conditioners, refrigerators and other air conditioning equipment.

BACKGROUND ART

is Refrigerants for use in refrigerating cycle apparatuses have been moving to HFC (hydrofluorocarbon)-related refrigerants (hereinafter, referred to as ‘HFC refrigerant’) having an ODP (Ozone Depletion Potential) of 0. However, the HFC refrigerants are very high in GWP. Accordingly, there have been being developed compressors using refrigerants that are low in ODP and GWP. Unfortunately, refrigerants being low in GWP are, in general, low in stability. Thus, there is a need for ensuring stability and reliability of the refrigerant for its long-term use in refrigerating cycle apparatuses for room air conditioners, automotive air conditioners, refrigerators and other air conditioning equipment.

With use of refrigerants composed principally of hydrofluoroolefin containing no chlorine atoms and being low in GWP and moreover having a double bond of carbon, there are problems as follows. Such refrigerants, having a characteristic of high decomposability at high temperatures, will be decomposed due to high temperatures when elevated to the high temperatures by over-compression or re-expansion. Therefore, these refrigerants are low in stability. Particularly when those refrigerants are used for long time in room air conditioners, automotive air conditioners, refrigerators and other air conditioning equipment, decomposition of the refrigerants due to high temperatures keeps occurring over long periods, giving rise to a need for measures against temperature increases of the refrigerants.

In a refrigerating cycle, a refrigerant evaporated by an evaporator is sucked into a compressor and compressed to a prescribed pressure by the compressor. During this process, the refrigerant changes in state largely from low to high pressure and from low to high temperature. Therefore, the compressor needs to be made up so that stability and reliability of the refrigerant can be ensured.

For example, PTL 1 discloses a compressor which uses a refrigerant of low GWP and which has a direct suction path for feeding the refrigerant directly to a suction port so that compression of the refrigerant sucked to inside of the compressor is started at as low temperatures as possible. With such an arrangement, temperature increases of the refrigerant before compression start are suppressed, compared with a case where the refrigerant is temporarily stored in a storage space such as a crankcase before being fed to a compression chamber. By virtue of the suppression of temperature increases before the compression start, the temperature of the refrigerant after its compression to the prescribed pressure by the compressor is lower than that of the case where the refrigerant is not directly fed to the suction port. As a result, decomposition of the refrigerant is inhibited, so that faults or life reduction of the compressor due to decomposition products (e.g., sludge) of the refrigerant is suppressed. That is, reliability and durability of the compressor are improved.

CITATION LIST Patent Literature

-   PTL 1: JP 2009-228473 A

SUMMARY OF INVENTION Technical Problem

However, even with suppression of temperature increases of the refrigerant before compression start, there are some cases where the temperature of the refrigerant after its compression to the prescribed pressure by the compressor becomes higher than necessary, so that the refrigerant may be decomposed. Among causes for this case is ‘re-expansion heating.’ The ‘re-expansion heating’ refers to a phenomenon that a high-pressure refrigerant under compression is leaked into a low-pressure space so as to be re-expanded to a high temperature in the low-pressure space so that the low-pressure refrigerant present in the low-pressure space is heated resultantly. By such re-expansion heating, the refrigerant having been compressed to a prescribed pressure becomes higher than necessary temperatures. Also, in the event of re-expansion heating, part of compression power (energy) spent to obtain a high-temperature, high-pressure refrigerant is used for heating of the low-temperature, low-pressure refrigerant, causing the compressor efficiency to lower.

As a method for suppressing such re-expansion heating due to leakage of the refrigerant under compression, it is conceivable that a refrigerating machine oil is fed to the refrigerant before compression start (suction process) so as to improve sealability of the compression chamber after the refrigerant has been enclosed therein. However, there is a problem that the refrigerant before compression start (suction process) is heated by higher-temperature oil than the refrigerant.

Accordingly, with an aim of solving the above-described problems, an object of the present invention is to provide a rotary compressor which uses a refrigerant of low GWP and which is capable of suppressing the re-expansion heating by improving the sealability of the compression chamber by using a refrigerating machine oil and moreover capable of suppressing the heating of the refrigerant by the refrigerating machine oil, thus the rotary compressor being excellent in reliability and durability and moreover high in efficiency.

Solution to Problem

In order to achieve the above object, the present invention has the following constitutions.

In order to solve the above-described problems, in one aspect of the present invention, there is provided a rotary compressor in which

a single refrigerant of hydrofluoroolefin having a double bond of carbon or a mixed refrigerant containing the hydrofluoroolefin is used, the rotary compressor comprising:

a compression chamber for compressing the refrigerant; and

a first compression-chamber oil feed path for feeding refrigerating machine oil to the compression chamber after the refrigerant has been enclosed therein.

A refrigerating machine oil is fed to the compression chamber after the refrigerant has been enclosed therein, by which the sealability of the compression chamber is improved so that the re-expansion heating due to leakage of the refrigerant under compression is suppressed and moreover heating of the refrigerant by the refrigerating machine oil is suppressed as compared with cases in which the refrigerating machine oil is fed in the suction process. As a result, the temperature of the refrigerant after its compression to a prescribed pressure becomes lower than those in cases where the refrigerating machine oil is fed in the suction process, thus decomposition of the refrigerant being inhibited.

As compared with a case where the refrigerating machine oil is fed in the suction process, the temperature of the refrigerant after its compression to a prescribed pressure becomes lower in the case where the refrigerating machine oil is fed to the compression chamber after the refrigerant has been enclosed therein. The reason of this is as follows.

The refrigerant under suction into the compression chamber (under suction process) is the lowest in temperature. When a high-temperature refrigerating machine oil is fed to such a refrigerant, the refrigerant is strongly heated because of a large temperature difference between the refrigerant and the refrigerating machine oil (as a result, decomposition of the refrigerant progresses to a large extent). In contrast to this, the refrigerant under compression increases in temperature of the refrigerant itself along with the compression, resulting in a small temperature difference from the fed refrigerating machine oil. In a case of the refrigerant further compressed to near the discharge pressure, the temperature of the refrigerant has become higher than the temperature of the fed refrigerating machine oil. Accordingly, heating of the refrigerant by the refrigerating machine oil can be suppressed more in the case where the refrigerating machine oil is fed to the compression chamber after the refrigerant has been enclosed therein (compression process). Thus, not by feeding the refrigerating machine oil in suction process but by feeding the refrigerating machine oil in compression process, heating of the refrigerant can be suppressed while the sealability of the compression chamber after the refrigerant has been enclosed therein can be improved by the refrigerating machine oil. In addition, desirably, the refrigerating machine oil is fed at such a timing that its temperature difference from the refrigerant becomes as small as possible.

Advantageous Effects of Invention

According to the present invention, in a rotary compressor, with use of a refrigerant being low in both ODP and GWP, temperature increases of the refrigerant, which could cause decomposition of the refrigerant, can be suppressed. As a result, there can be provided a rotary compressor being excellent in reliability and durability and having high efficiency with considerations given to the global environment.

BRIEF DESCRIPTION OF DRAWINGS

The above aspects and features of the present invention will become more apparent from the following description of preferred embodiments thereof with reference to the accompanying drawings, and wherein:

FIG. 1 is a sectional view of a scroll compressor according to Embodiment 1 of the invention;

FIG. 2 is a partly enlarged sectional view of a compression mechanism of the scroll compressor according to Embodiment 1;

FIG. 3 is a view showing a plurality of states of a turning scroll of the scroll compressor according to Embodiment 1;

FIG. 4 is a partly enlarged sectional view of a compression mechanism of a scroll compressor according to Embodiment 2 of the invention;

FIG. 5 is a view showing a plurality of states of a turning scroll of the scroll compressor according to Embodiment 2;

FIG. 6 is a sectional view of a rotary compressor according to Embodiment 3 of the invention;

FIG. 7 is an enlarged sectional view of a compression mechanism of the rotary compressor according to Embodiment 3;

FIG. 8 is an assembly structural view of the compression mechanism of the rotary compressor according to Embodiment 3; and

FIG. 9 is a view showing a plurality of states of the compression mechanism of the rotary compressor according to Embodiment 3.

DESCRIPTION OF EMBODIMENTS

In a rotary compressor according to one aspect of invention, a single refrigerant of hydrofluoroolefin having a double bond of carbon or a mixed refrigerant containing the hydrofluoroolefin is used, the rotary compressor comprises a compression chamber for compressing the refrigerant; and a first compression-chamber oil feed path for feeding refrigerating machine oil to the compression chamber after the refrigerant has been enclosed therein. By the use of a refrigerant being low in both ODP and GWP, effects on the global environment can be suppressed. Also, with an aim of solving the problem that a single refrigerant (or mixed refrigerant) of hydrofluoroolefin having a double bond of carbon is easily decomposable at high temperatures, the refrigerating machine oil is fed to the compression chamber after the refrigerant has been enclosed therein. By doing so, sealability of the compression chamber is improved, so that the re-expansion heating due to leakage of the refrigerant under compression is suppressed and moreover temperature increases of the refrigerant due to the feeding of the refrigerating machine oil are suppressed as compared with cases in which the refrigerating machine oil is fed in the suction process (before the refrigerant is enclosed in the compression chamber). As a result, the temperature of the refrigerant after its compression to a prescribed pressure becomes lower, as compared with cases where the refrigerating machine oil is fed in the suction process, so that decomposition of the refrigerant is inhibited. Thus, there can be provided a rotary compressor being excellent in reliability and durability and having high efficiency with considerations given to the global environment.

The rotary compressor may be configured that the first compression-chamber oil feed path is intermittently dosed. The refrigerating machine oil can be fed to the compression chamber at such an optimum timing and an optimum quantity that improvement of the sealability of the compression chamber as well as suppression of temperature increases of the refrigerant due to the feeding of the refrigerating machine oil can be effectively fulfilled. As a result, temperature increases of the refrigerant due to the feeding of the refrigerating machine oil and re-expansion heating due to the leakage of the refrigerant can be suppressed further securely.

In case the compression chamber is defined between a stationary scroll and a turning scroll by the stationary scroll and the turning scroll being engaged with each other, each of the stationary scroll and the turning scroll including, an end plate and a lap being a volute-shaped wall formed on the end plate, the rotary compressor may comprise an oil storage section for storing the refrigerating machine oil therein; and at least one or more second compression-chamber oil feed paths for feeding the refrigerating machine oil from the oil storage section to the compression chamber, and wherein at least one of the second compression-chamber oil feed paths is the first compression-chamber oil feed path.

Generally, with a rotary compressor which includes a plurality of compression chambers and in which the refrigerant in the plurality of compression chambers is compressed simultaneously, in a case where the refrigerant being under compression and having been compressed to some extent of high pressure leaks to the lower-pressure side compression chamber, the leak of the refrigerant is more likely to occur (so-called internal leakage occurs) not in the compression chamber under suction of the refrigerant but in the compression chamber being under one-process-later compression process. In such a case, re-expansion of the leaked refrigerant causes not only heating of the refrigerant in the leakage-destination compression chamber but also pressure increases in the leakage-destination compression chamber. As a result of such internal leakage, the refrigerant temperature increases. As a countermeasure for this, providing at least one second compression-chamber oil feed path for feeding the refrigerating machine oil to the compression chamber makes it possible to improve the sealability of the compression chamber involved in occurrence of the internal leakage, which particularly contributes to temperature increases of the refrigerant, by using an optimum quantity of the refrigerating machine oil. Also, by the use of an optimum quantity, of the refrigerating machine oil, heating of the refrigerant due to excess refrigerating machine oil, which could be caused by the feeding of excessive quantities of the refrigerating machine oil, can also be suppressed.

In case the compression chamber includes a first compression chamber formed outside the lap of the turning scroll and a second compression chamber formed inside the lap of the turning scroll, in comparison between the first compression chamber and the second compression chamber, a feed rate of the refrigerating machine oil to one compression chamber having a longer leak length may be larger than a feed rate of the refrigerating machine oil to the other compression chamber. Since the feed rate of the refrigerating machine oil can be optimized to improve the sealability in correspondence to the length of the leakage portion of the compression chamber, heating of the refrigerant due to excess refrigerating machine oil, which could be caused by feeding of excessive quantities of refrigerating machine oil, can also be suppressed.

In case the compression chamber includes a first compression chamber formed outside the lap of the turning scroll, and a second compression chamber formed inside the lap of the turning scroll, in comparison between the first compression chamber and the second compression chamber, a feed rate of the refrigerating machine oil to one compression chamber having a higher capacity change rate may be larger than a feed rate of the refrigerating machine oil to the other compression chamber. By an optimum quantity of the refrigerating machine oil, the sealability of the compression chamber, in which leakage of the refrigerant is more likely to occur because of a large pressure difference from the lower-pressure side compression chamber, can be improved. Heating of the refrigerant due to excess refrigerating machine oil, which could be caused by feeding of excessive quantities of refrigerating machine oil, can also be suppressed.

The first compression-chamber oil feed path may comprise a lead-in path part provided in a back face of the turning scroll so as to allow the refrigerating machine oil to be led in from the oil storage section; an in-lap oil feed path part which is provided inside the lap of the turning scroll so as to be communicated with the lead-in path part and which has an opening in a lap top face; and a recess portion which is provided in the end plate of the stationary scroll and which is intermittently communicated with the opening of the in-lap oil feed path part. As a result of this, it becomes possible to feed the refrigerating machine oil in particular periods to the compression chamber after the refrigerant has been enclosed therein, while it becomes easier to achieve control of the feed rate of the refrigerating machine oil. Further, back flow of the compressed refrigerant to the first compression-chamber oil feed path can be prevented, making it possible to realize a scroll compressor of high reliability.

The refrigerant may contain at least one of tetrafluoropropene or trifluoropropene, which is a kind of hydrofluoroolefin, and the refrigerant has a global warming potential within a range of 5 to 750, desirably 5 to 350. With such a refrigerant, there can be provided a rotary compressor of low environmental load, high reliability and high efficiency.

The refrigerant may contain, as a principal ingredient, tetrafluoropropene or trifluoropropene, which is a kind of hydrofluoroolefin, and difluoromethane and pentafluoroethane are mixed in the refrigerant so that its global warming potential falls within a range of 5 to 750, desirably 5 to 350. With such a refrigerant, smaller environmental loads are involved and moreover the flow velocity can be suppressed to lower the temperature. Thus, a rotary compressor of high reliability and high efficiency can be provided effectively.

The refrigerating machine oil may be (1) polyoxyalkylene glycol, (2) polyvinyl ether, (3) poly(oxy)alkylene glycol or copolymer of its monoether and polyvinyl ether, (4) synthetic oil containing an oxygenated compound of polyol esters and polycarbonates, (5) synthetic oil containing alkylbenzenes as a principal ingredient, or (6) synthetic oil containing α-olefins as a principal ingredient. With such refrigerating machine oil, a rotary compressor of high reliability and high efficiency can be provided effectively.

Hereinbelow, embodiments of the present invention will be described with reference to the accompanying drawings. It is noted that the invention is not limited by these embodiments.

In compressors according to three embodiments of the invention described below, a single refrigerant of hydrofluoroolefin having a double bond of carbon or a mixed refrigerant containing the hydrofluoroolefin is used.

Embodiment 1

FIG. 1 is a longitudinal sectional view of a scroll compressor according to Embodiment 1 of the invention. FIG. 2 is a partly enlarged sectional view of a compression mechanism shown in FIG. 1. FIG. 3 is a view showing a plurality of states of a turning scroll of the compression mechanism. The scroll compressor will be described below in terms of its operation and function.

The scroll compressor of this Embodiment 1 has a dosed container 1 as shown in FIG. 1. The scroll compressor also has a compression mechanism 2, a motor section 3 and an oil storage section 20 inside the closed container 1. The compression mechanism 2 is made up of a main bearing member 11 fixed to the closed container 1 by welding or shrinkage fit or the like, a shaft 4 supported by the main bearing member 11, a stationary scroll 12 fixed onto the main bearing member 11 with a bolt or the like, and a turning scroll 13 placed between the main bearing member 11 and the stationary scroll 12 so as to be engaged with the stationary scroll 12.

The stationary scroll 12 includes an end plate 12 a, and a lap 12 b that is a volute-shaped wall formed on the end plate 12 a, while the turning scroll 13 includes an end plate 13 a, and a lap 13 b that is a volute-shaped wall formed on the end plate 13 a. An automatic constraint mechanism 14, including Oldham's ring or the like for preventing self-rotation of the turning scroll 13 and for guiding in a way that the turning scroll 13 driven by the shaft 4 makes motion on a circular orbit is provided between the turning scroll 13 and the main bearing member 11. An eccentric shaft part 4 a located at an upper end of the shaft 4 makes the turning scroll 13 eccentrically turned, by which the circular-orbit turning motion of the turning scroll 13 is fulfilled.

With the construction shown above, a compression chamber 15 defined between the stationary scroll 12 and the turning scroll 13 is moved from outer peripheral side toward center while reducing its capacity. Via a suction pipe 16 communicating with outside of the closed container 1 and a suction port 17 in an outer peripheral part of the stationary scroll 12, a refrigerant (gas) is sucked into the compression chamber 15 (suction process). After the compression chamber 15 is closed by turning motion of the turning scroll 13 (after the refrigerant is enclosed in the compression chamber 15), the refrigerant is compressed (compression process). The refrigerant having reached a prescribed pressure by the compression pushes and opens a lead valve 19 provided at a discharge hole 18 in a central portion of the stationary scroll 12, thus the refrigerant moving from the compression chamber 15 via the discharge hole 18 into the closed container 1.

Also, a pump 25 is provided at the other end of the shaft 4. The pump 25 is so placed that its suction opening is present within the oil storage section 20 provided at a bottom portion of the closed container 1. Since the pump 25 is driven in synchronism with the compression mechanism 2, the pump 25 is enabled to securely suck up refrigerating machine oil 6 stored in the oil storage section 20, and further stably feed the oil to the compression mechanism 2, irrespective of pressure conditions or operating speed. The oil 6 sucked up by the pump 25 is passed through an oil feed hole 26 extending through inside the shaft 4 so as to be fed to the compression mechanism 2. In addition, by removing foreign matters from within the oil 6 with an oil filter or the like before or after the sucking-up by the pump 25, mixing of foreign matters into the compression mechanism 2 can be prevented, so that the reliability of the compressor can be further improved.

A pressure of the oil 6 introduced into the compression mechanism 2, being generally equal to a discharge pressure of the scroll compressor, serves as a back pressure source for the turning scroll 13. That is, the oil 6 fulfills a role of pressing a back face (surface facing the main bearing member 11) of the turning scroll 13 to push the turning scroll 13 against the stationary scroll 12. As a result of this, the turning scroll 13 is kept in contact with the stationary scroll 12 without separating from the stationary scroll 12 and without partly contacting the stationary scroll 12. Thus, the compression mechanism 2 is enabled to fulfill specified compression power with stability. Further, part of the oil 6 enters, by the feed pressure or deadweight, into a fitting portion between the eccentric shaft part 4 a and the turning scroll 13 as well as to a bearing portion 66 provided between the shaft 4 and the main bearing member 11 and serves for lubrication. The oil 6 after the lubrication falls down to return to the oil storage section 20 as indicated by arrows in FIG. 2.

Also, a seal member 78 is placed between the back face of the turning scroll 13 and the main bearing member 11 so that a high-pressure region 30 is defined inside the seal member 78 while a back pressure chamber 29 is defined outside the seal member 78. Since a pressure of the high-pressure region 30 and a pressure of the back pressure chamber 29 can be fully isolated from each other, it becomes implementable to stably control the pressure on the back face of the turning scroll 13.

In a portion 12 c of the end plate 12 a between laps 12 b of the stationary scroll 12, a recess portion 12 d is formed. Further, an in-lap oil feed path 55 is formed in the turning scroll 13. The in-lap oil feed path 55 is communicated with the back pressure chamber 29 via one opening 55 a. Then, the back pressure chamber 29 is communicated with the oil storage section 20 via a lead-in path 54 provided on the back face side of the turning scroll 13 and the oil feed hole 26 provided in the shaft 4. Meanwhile, the other opening 55 b of the in-lap oil feed path 55 is formed in a top face of the lap 13 a that makes sliding contact with the end plate 12 a of the stationary scroll 12. The opening 55 b of the in-lap oil feed path 55 is moved relative to the stationary scroll 12 by the turning motion of the turning scroll 13 so as to draw a circular turning locus as shown by broken line in FIG. 3.

FIG. 3 shows a plurality of states of the turning scroll 13 engaged with the stationary scroll 12, more specifically, states of the turning scroll 13 individually differing by steps of 90° from one another. As shown in FIG. 3, the compression chamber 15 formed by the stationary scroll 12 and the turning scroll 13 includes a first compression chamber 15 a formed outside the lap 13 a of the turning scroll 13, and a second compression chamber 15 b formed inside the lap 13 a. The first compression chamber 15 a and the second compression chamber 15 b are moved each by turning motion of the turning scroll 13 toward the center while reducing their capacities. When the refrigerant in the compression chamber 15 has reached the discharge pressure and moreover the compression chamber 15 and the discharge hole 18 are communicated with each other, the refrigerant in the compression chamber 15 pushes and opens the lead valve 19, thus moving into a discharge chamber 31.

As shown in FIG. 3, the opening 55 b of the in-lap oil feed path 55 and the recess portion 12 d formed at the portion 12 c of the end plate 12 a of the stationary scroll 12 are intermittently communicated with each other. As a result of this, the in-lap oil feed path 55 and the second compression chamber 15 b are intermittently communicated with each other via the recess portion 12 d.

The following description is given by focusing on the second compression chamber 15 b. As shown in FIG. 3( a), when the second compression chamber 15 b formed on the outermost side of the turning scroll 13 and the suction port 17 are communicated with each other, introduction of the refrigerant into the second compression chamber 15 b is started (start of suction process). Then, as shown in FIG. 3( c), the second compression chamber 15 b is closed by turning motion of the turning scroll 13, so that the refrigerant is enclosed within the second compression chamber 15 b (start of compression process). Thereafter, as shown in FIG. 3( d), the opening 55 b of the in-lap oil feed path 55 is communicated with the second compression chamber 15 b via the recess portion 12 d by turning motion of the turning scroll 13, and then the oil 6 is fed from the back pressure chamber 29 via the in-lap oil feed path 55 to the second compression chamber 15 b after the refrigerant has been enclosed therein. In contrast to this, with the opening 55 b and the recess portion 12 d not communicated with each other as shown in FIG. 3( a)-(c), oil is scarcely fed from the back pressure chamber 29 to the second compression chamber 15 b. Thus, by making the opening 55 b of the in-lap oil feed path 55 and the second compression chamber 15 b intermittently communicated with each other via recess portion 12 d of the stationary scroll 12, the oil 6 is intermittently fed to the second compression chamber 15 b via the in-lap oil feed path 55. It is noted that the reason of feeding the oil 6 to the second compression chamber 15 b will be described later.

As described above, according to this Embodiment 1, use of a single refrigerant of hydrofluoroolefin or a mixed refrigerant containing the hydrofluoroolefin, being low in ODP and GWP, makes it possible to suppress is effects on the global environment. Also, by feeding the oil 6 to the second compression chamber 15 b after the refrigerant has been enclosed therein (compression process), the temperature of the refrigerant after its compression to a prescribed pressure becomes lower, as compared with cases where the oil 6 is fed in the suction process (i.e., in a state of being communicated with the suction port 17).

The reason that the refrigerant temperature after the compression the prescribed pressure is lower in feeding of the oil 6 to the second compression chamber 15 b in the compression process than in feeding of the oil 6 to the second compression chamber 15 b in the suction process is as follows.

The refrigerant during suction to the second compression chamber 15 b (in the suction process) is the lowest in its temperature. Feeding a high-temperature oil 6 to such a refrigerant causes the refrigerant to be strongly heated because of a large temperature difference between the refrigerant and the oil 6 (as a result, decomposition of the refrigerant progresses to a large extent). In contrast to this, the refrigerant under compression has increased in temperature of the refrigerant itself along with the compression, having a small temperature difference from the fed oil 6. In a case of the refrigerant further compressed to near the discharge pressure, the refrigerant temperature becomes higher than the temperature of the fed oil 6. Accordingly, heating of the refrigerant by the oil 6 can be suppressed more in the case where the oil 6 is fed to the second compression chamber 15 b after the refrigerant has been enclosed therein (compression process). Thus, not by feeding the oil 6 in suction process but by feeding the oil 6 in compression process, heating of the refrigerant can be suppressed while the sealability of the second compression chamber 15 b after the refrigerant has been enclosed therein can be improved by the oil 6. In addition, desirably, the oil 6 is fed at such a timing that a temperature difference of the oil 6 from the refrigerant is as small as possible.

Further, since the sealability of the second compression chamber 15 b (between the end plate 12 a of the stationary scroll 12 and the lap 13 b of the turning scroll 13 and between the lap 12 b and the end plate 13 a) is improved by the oil 6, re-expansion heating, i.e. leakage of the refrigerant from the second compression chamber 15 b, can be suppressed.

As a result, temperature increases of the refrigerant are suppressed, so that decomposition of the refrigerant is inhibited. Thus, there can be provided a rotary compressor being excellent in reliability and durability and having high efficiency with considerations given to the global environment.

Further, the oil 6 in the back face of the turning scroll 13 can be fed to the second compression chamber 15 b via the in-lap oil feed path 55 and the recess portion 12 d when the turning scroll 13 is in a particular phase (i.e., when the shaft 4 is at a particular turning angle). That is, the oil 6 can be fed to the second compression chamber 15 b at such an optimum timing and an optimum quantity that improvement of the sealability of the second compression chamber 15 b as well as suppression of temperature increases of the refrigerant by feeding of the oil 6 can be fulfilled effectively. As a result, temperature increases of the refrigerant due to the feeding of the oil 6 and the re-expansion heating due to the leakage of the refrigerant can be suppressed more securely.

Now the reason of feeding the oil 6 to the second compression chamber 15 b via the in-lap oil feed path 55 is described below. First, configuration of the laps included in the stationary scroll 12 and the turning scroll 13 is described. In this embodiment, the volute shape of the laps of the stationary scroll and the turning scroll is defined by an involute curve. Given an involute angle of θ and a basic circle radius of a, an involute curve can be expressed by the following function in the Cartesian coordinate system:

x=a(cos θ+θ sin θ)

y=a(sin θ+θ cos θ)  (Eq. 1)

A curve expressed by Equation 1 is taken as a reference curve. Out of two envelope curves drawn by the reference curve as a result of turning with a turning radius of ε, the outer envelope curve is expressed by the following function:

x=a(cos(θ−ε/a)+θ sin(θ−ε/a))

y=a(sin(θ−ε/a)+θ cos(θ−ε/a))  (Eq. 2)

Similarly, the inner envelope curve is expressed by the following function:

x=a(cos(θ+ε/a)+θ sin(θ+ε/a))

y=a(sin(θ+ε/a)+θ cos(θ+ε/a))  (Eq. 3)

By defining an outer surface of the lap of either one of the stationary scroll 12 or the turning scroll 13 with the above-described function of the reference curve, and by defining an inner surface of the other lap combined with the above lap by using the above-described function of the outer envelope curve, it follows that a plurality of minimum radial clearances on the inner surface side of the lap 13 b of the turning scroll 13 or a plurality of minimum radial clearances on the outer surface side of the lap 13 b of the turning scroll 13, both of which are formed simultaneously by engagement of the lap of the stationary scroll and the lap of the turning scroll with each other, become equal to one another. In this embodiment, an asymmetrical compression chamber 15 is realized by forming the lap 12 b of the stationary scroll 12 and the lap 13 b of the turning scroll 13 so that their numbers of turns differ from each other, with an aim of enlarging the capacity of the compression chamber 15.

Since an asymmetrical compression chamber is formed, capacity change rate of the second compression chamber 15 b formed on the inner surface side of the lap 13 b of the turning scroll 13 is larger than capacity change rate of the first compression chamber 15 a formed on the outer surface side of the lap 13 b. The second compression chamber 15 b having the larger capacity change rate increases in refrigerant pressure more rapidly than the first compression chamber 15 a, resulting in a larger pressure difference from the lower-pressure side compression chamber 15. Because of this, leakage of the refrigerant to the lower-pressure side compression chamber 15 from the second compression chamber 15 b by passing through between the lap and the end plate is more likely to occur, making it necessary to improve the sealability.

Therefore, in this Embodiment 1, the in-lap oil feed path 55 and the recess portion 12 d are properly provided so that as much oil 6 as possible is fed to the second compression chamber 15 b of larger capacity change rate. As a result, leakage of the refrigerant from the second compression chamber 15 b to the lower-pressure side compression chamber 15 is suppressed, so that the re-expansion heating of the refrigerant in the lower-pressure side compression chamber 15 is suppressed and moreover pressure increases due to internal leakage can be suppressed. As a result, temperature increases of the refrigerant, which is easily decomposable at high temperatures and which is used for the scroll compressor of Embodiment 1, can be suppressed.

Furthermore, it is also allowable that another compression-chamber oil feed path for feeding the oil 6 to the first compression chamber 15 a (a second compression-chamber oil feed path different from the first compression-chamber oil feed path) is provided so that a smaller quantity of oil 6 than that of oil 6 intermittently fed to the second compression chamber 15 b is fed to the first compression chamber 15 a via the another compression-chamber oil feed path. As such another compression-chamber oil feed path, for example, a compression-chamber oil feed path 57 shown in FIG. 2 is provided. The compression-chamber oil feed path 57 is formed in the turning scroll 13. One opening of the compression-chamber oil feed path 57 is formed in the top face of the lap 13 b. The other opening is communicated with the oil storage section 20 via the lead-in path 54 provided in the back face of the turning scroll 13, the oil feed hole 26 provided in the shaft 4 and the like. As a result of this, a small quantity of oil 6 can be fed through the clearance between the end plate 12 a of the stationary scroll 12 and the top face of the lap 13 b of the turning scroll 13.

In this case also, re-expansion heating of the refrigerant can be suppressed and moreover pressure increases due to internal leakage can be suppressed. Further, since the feed rate of the oil 6 to the second compression chamber 15 b of higher capacity change rate is larger than the feed rate of the oil 6 to the first compression chamber 15 a, the sealability of the compression chamber, which is liable to leakage of the refrigerant because of a large pressure difference from the lower-pressure side compression chamber 15, can be improved by an optimum quantity of oil. As a result of this, heating of the refrigerant due to excessive refrigerating machine oil, which could be caused by feeding of excessive quantities of refrigerating machine oil, can also be suppressed.

Besides, with respect to the quantity of oil 6 fed to the second compression chamber 15 b, it is also allowable that a quantity of oil smaller than the quantity of oil fed after enclosing of the refrigerant (after closure of the second compression chamber 15 b) is fed before the enclosing of the refrigerant (before the second compression chamber 15 b starts to be closed) or during the enclosing of the refrigerant (during a period from a start of closure of the second compression chamber 15 b until its complete closure). That is, only if most part of the necessary quantity of oil 6 is fed after the enclosing of the refrigerant, temperature increases of the refrigerant, i.e. decomposition of the refrigerant, can be suppressed.

Embodiment 2

FIG. 4 is a partly enlarged sectional view of a compression mechanism of a scroll compressor according to Embodiment 2 of the invention. FIG. 5 is a view showing a plurality of states of a turning scroll. Component members other than a compression-chamber oil feed path 56 are similar to those of above-described Embodiment 1. In FIGS. 4 and 5, the same component members as in FIGS. 2 and 3 are designated by the same reference signs. Also, the following description is made about the compression-chamber oil feed path 56 alone, and description of the other component members is omitted.

As shown in FIG. 4, in the scroll compressor of this Embodiment 2, a compression-chamber oil feed path 56 is formed in the end plate 13 a of the turning scroll 13. The compression-chamber oil feed path 56 communicates the back pressure chamber 29 and the first compression chamber 15 a formed on the outer surface side of the lap 13 b of the turning scroll 13 with each other. While the turning scroll 13 is in a state shown in FIG. 5( b), the compression-chamber oil feed path 56 is communicated with the first compression chamber 15 a so that the oil 6 is fed to the first compression chamber 15 a. On the other hand, while the turning scroll 13 is in a state shown in FIG. 5( a), 5(c) or 5(d), the compression-chamber oil feed path 56 is closed by the end plate 12 a of the stationary scroll 12, so that the oil 6 is not fed to the first compression chamber 15 a. In a scroll compressor in which the capacity of the compression chamber reduces along with movement from outer periphery toward center, a compression chamber located on the outer side is larger in capacity than a compression chamber located on the central side. Therefore, with respect to a leak length (in other words, necessary seal length), which is a length of a portion through which the refrigerant leaks from a high-pressure side compression chamber of smaller capacity to a low-pressure side compression chamber of larger capacity, the length of the first compression chamber 15 a formed on the outer side of the lap 13 b of the turning scroll 13 is longer than the length of the second compression chamber 15 b formed on the inner side. Accordingly, the oil 6 is fed to the first compression chamber 15 a of longer leak length via the compression-chamber oil feed path 56 in a quantity larger than the quantity of oil 6 fed to the second compression chamber 15 b, by which the first compression chamber 15 a of longer leak length is sealed enough. As a result of this, temperature increases of the refrigerant, which is easily decomposable at high temperatures, are suppressed.

According to this Embodiment 2, re-expansion heating of the refrigerant and pressure increases due to internal leakage can be suppressed, and moreover making the feed rate of oil 6 to the first compression chamber 15 a of longer leak length larger than the feed rate of oil 6 to the second compression chamber 15 b makes it possible to optimize the feed rate of oil 6 for improvement of the sealability in correspondence to the length of the leakage portion of the compression chamber. As a result, heating of the refrigerant due to excessive refrigerating machine oil, which could be caused by feeding of excessive quantities of refrigerating machine oil, can also be suppressed.

Embodiment 3

FIG. 6 is a longitudinal sectional view of a rotary compressor according to Embodiment 3 of the invention. FIG. 7 is an enlarged sectional view of a compression mechanism of the rotary compressor. FIG. 8 is an assembly structural view of the compression mechanism of the rotary compressor. FIG. 9 is a view showing a plurality of states of the compression mechanism of the rotary compressor. In the rotary compressor, as shown in FIGS. 6 and 7, an electric motor 102 and a compression mechanism 103, being coupled together via a crankshaft 131, are housed within the closed container 101. The compression mechanism 103 includes: a cylinder 130; a suction chamber 149 and a compression chamber 139 defined by an end plate 134 of an upper bearing 134 a and an end plate 135 of a lower bearing 135 a for closing both end faces of the cylinder 130; a piston 132 placed within the cylinder 130; and a vane 133 which is in contact with an outer peripheral surface of the piston 132 to divide the cylinder 130 into the suction chamber 149 and the compression chamber 139. The piston 132 is fitted to an eccentric portion 131 a of the crankshaft 131 supported by the upper bearing 134 a and the lower bearing 135 a so as to be eccentrically rotated by the crankshaft 131. The vane 133 is so constructed as to make reciprocating motion toward the piston 132 in correspondence to eccentric rotation of the piston 132 so as to maintain the contact with the outer peripheral surface of the eccentrically rotating piston 132.

In the crankshaft 131, an oil hole 141 is formed along a center axis for drawing up oil from the oil storage section 20. Oil feed holes 142, 143 communicated with the oil hole 141 are provided at portions of the crankshaft 131 facing the upper bearing 134 a and the lower bearing 135 a, respectively. Also, an oil feed hole 144 communicated with the oil hole 141 and an oil groove 145 communicated with the oil feed hole 144 are formed at portions of the eccentric portion 131 a of the crankshaft 131 facing the piston 132.

Meanwhile, a suction port 140 for sucking a gaseous refrigerant into the suction chamber 149 is formed in the cylinder 130. As a sliding-contact portion of the piston 132 which is in sliding contact with an inner peripheral surface of the cylinder 130 passes through the suction port 140 so as to be separated from the suction port 140, the suction chamber 149 expands gradually, causing the refrigerant to be sucked into the suction chamber 149 through the suction port 140. In the upper bearing 134 a is a discharge port 138 opened for discharging out the refrigerant from the compression chamber 139. The discharge port 138 is formed as a hole having a circular cross section extending through the upper bearing 134 a. In the top face of the discharge port 138, a delivery valve 136 which opens upon reception of a more than specified pressure, and a cap muffler 137 for covering the delivery valve 136, are provided.

As the sliding-contact portion of the piston 132 in sliding contact with the inner peripheral surface of the cylinder 130 approaches the discharge port 138 more and more, the compression chamber 139 is reduced gradually. When the refrigerant within the compression chamber 139 is compressed to a specified pressure or more, the delivery valve 136 is opened. When the delivery valve 136 is opened, the refrigerant flows out through the discharge port 138 so as to be discharged out into the closed container 101 by the cap muffler 137.

On the other hand, a space 146 surrounded by the eccentric portion 131 a of the crankshaft 131, the end plate 134 of the upper bearing 134 a and the inner peripheral surface of the piston 132, and a space 147 surrounded by the eccentric portion 131 a of the crankshaft 131, the end plate 135 of the lower bearing 135 a and the inner peripheral surface of the piston 132, are formed, it is leaked into those spaces 146, 147 from the oil hole 141 via the oil feed holes 142, 143. Pressures of these spaces 146, 147, nearly normally higher than the pressure inside the compression chamber 139, are generally equal to the discharge pressure.

Also, the height of the cylinder 130 is set slightly larger than the height of the piston 132 so that the piston 132 is enabled to make sliding contact inside the cylinder 130. As a result, there are clearances between the end face of the piston 132 and the end plate 134 of the upper bearing 134 a as well as the end plate 135 of the lower bearing 135 a. Oil in the spaces 146, 147 leaks via these clearances into the compression chamber 139.

In the rotary compressor constructed as described above, as shown hi FIG. 8, a recess-shaped compression-chamber oil feed path 155 is provided in the end plate 135 of the lower bearing 135 a. FIG. 9 shows a positional relationship between the piston 132 and the oil feed path 155, as viewed in a center-axis direction of the crankshaft 131. As shown in left, lower part of FIG. 9, oil is fed to the compression chamber 139 at range of a crank angle of the crankshaft 131 that an inlet 155 a of the compression-chamber oil feed path 155 and the inside of the piston 132 are communicated with each other as well as an outlet 155 b of the oil feed path 155 and the compression chamber 139 are communicated with each other. In this case, by providing the compression-chamber oil feed path 155 in such a manner that the inlet 155 a and the outlet 155 b differ from each other in terms of angular position with respect to a crankshaft center, it becomes achievable to determine such a crank angle that oil is allowed to flow into the inlet 155 a. As a result, the degree of freedom for the position of the outlet 155 b is increased. Thus, it becomes possible to provide the outlet 155 b of the compression-chamber oil feed path 155 near a refrigerant-leaking place.

Also, as shown in left, lower part of FIG. 9, by providing the outlet 155 b of the oil feed path 155 at a position near a contact point between the piston 132 and the cylinder 130 in the compression chamber 139, leakage of the refrigerant through between the piston 132 and the cylinder 130 can be suppressed with a necessary, minimum quantity of oil. Thus, temperature increases of the refrigerant, which is easily decomposable at high temperatures, are suppressed.

According to this Embodiment 3, with use of a refrigerant being low in both ODP and GWP, effects on the global environment can be reduced. Also, by feeding the oil to the compression chamber 139 after the refrigerant has been enclosed therein, re-expansion heating of the refrigerant is suppressed and moreover heating of the refrigerant by the refrigerating machine oil is suppressed, as compared with cases in which the refrigerating machine oil is fed in the suction process (before the refrigerant is enclosed in the compression chamber). As a result, decomposition of the refrigerant is inhibited.

Hereinabove, rotary compressors of Embodiments 1 to 3 have been described. In the rotary compressors of Embodiments 1 to 3, a single refrigerant of hydrofluoroolefin having a double bond of carbon or a mixed refrigerant containing the hydrofluoroolefin is used. As this mixed refrigerant, a refrigerant resulting from mixing hydrofluoroolefin with hydrofluorocarbon having no double bond of carbon may also be used.

Further, a mixed refrigerant of tetrafluoropropene (HFO1234yf or HFO1234ze) or trifluoropropene (HFO1243zf), which is a kind of hydrofluoroolefin, and difluoromethane (HFC32), which is a kind of hydrofluorocarbon, may also be used.

Further, a mixed refrigerant of tetrafluoropropene (HFO1234yf or HFO1234ze) or trifluoropropene (HFO1243zf), which is a kind of hydrofluoroolefin, and pentafluoroethane (HFC125), which is a kind of hydrofluorocarbon, may also be used.

Still further, a mixed refrigerant composed of three components resulting from mixing together tetrafluoropropene (HFO1234yf or HFO1234ze) or trifluoropropene (HFO1243zf), which is a kind of hydrofluoroolefin, pentafluoroethane (HFC125), which is a kind of hydrofluorocarbon, and difluoromethane (HFC32), may also be used.

Preferably, those mixed refrigerants described above are blended in such a two-component or three-component mixing that the GWP falls within a range of 5 to 750, desirably 5 to 350.

Further, preferably usable as the refrigerating machine oil to be used for the rotary compressor according to the invention are (1) polyoxyalkylene glycols, (2) polyvinyl ethers, (3) poly(oxy)alkylene glycol or copolymers of its monoether and polyvinyl ether, or (4) synthetic oils containing an oxygenated compound of polyol esters and polycarbonates, (5) synthetic oils containing alkylbenzenes as a principal ingredient, or (6) synthetic oils containing α-olefins as a principal ingredient.

Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Such Changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom.

The entire disclosure of Japanese Patent Application No. 2010-214877 filed on Sep. 27, 2010, including specification, claims, drawings, and summary are incorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

As described above, according to the present invention, even with use of a single refrigerant of hydrofluoroolefin having a double bond of carbon or a mixed refrigerant containing the hydrofluoroolefin, there can be realized a rotary compressor of high reliability, high durability and high efficiency. Therefore, the invention is applicable also to use in air conditioners, heat-pump water heaters, refrigerator-freezers, dehumidifiers or the like including rotary compressors.

REFERENCE SIGNS LIST

-   12 stationary scroll -   12 a end plate -   12 b lap -   12 d recess portion -   13 turning scroll -   13 a end plate -   13 b lap -   14 automatic constraint mechanism -   15 compression chamber -   15 a first compression chamber -   15 b second compression chamber -   17 suction port -   18 discharge hole -   19 lead valve -   20 oil storage section -   29 back pressure chamber -   30 high-pressure region -   55 in-lap oil feed path -   56 compression-chamber oil feed path -   130 cylinder -   131 crankshaft -   133 vane -   134 a upper bearing -   135 a lower bearing -   139 compression chamber -   141 oil hole -   155 compression-chamber oil feed path 

1. A rotary compressor in which a single refrigerant of hydrofluoroolefin having a double bond of carbon or a mixed refrigerant containing the hydrofluoroolefin is used, the rotary compressor comprising: a compression chamber for compressing the refrigerant; and a first compression-chamber oil feed path for feeding refrigerating machine oil to the compression chamber after the refrigerant has been enclosed therein.
 2. The rotary compressor according to claim 1, wherein the first compression-chamber oil feed path is intermittently closed.
 3. The rotary compressor according to claim 1, wherein the compression chamber is defined between a stationary scroll and a turning scroll by the stationary scroll and the turning scroll being engaged with each other, each of the stationary scroll and the turning scroll including an end plate and a lap being a volute-shaped wall formed on the end plate, the rotary compressor further comprising: an oil storage section for storing the refrigerating machine oil therein; and at least one or more second compression-chamber oil feed paths for feeding the refrigerating machine oil from the oil storage section to the compression chamber, and wherein at least one of the second compression-chamber oil feed paths is the first compression-chamber oil feed path.
 4. The rotary compressor according to claim 3, wherein the compression chamber includes a first compression chamber formed outside the lap of the turning scroll, and a second compression chamber formed inside the lap of the turning scroll, and in comparison between the first compression chamber and the second compression chamber, a feed rate of the refrigerating machine oil to one compression chamber having a longer leak length is larger than a feed rate of the refrigerating machine oil to the other compression chamber.
 5. The rotary compressor according to claim 3, wherein the compression chamber includes a first compression chamber formed outside the lap of the turning scroll, and a second compression chamber formed inside the lap of the turning scroll, and in comparison between the first compression chamber and the second compression chamber, a feed rate of the refrigerating machine oil to one compression chamber having a higher capacity change rate is larger than a feed rate of the refrigerating machine oil to the other compression chamber.
 6. The rotary compressor according to claim 3, wherein the first compression-chamber oil feed path comprises: a lead-in path part provided in a back face of the turning scroll so as to allow the refrigerating machine oil to be led in from the oil storage section; an in-lap oil feed path part which is provided inside the lap of the turning scroll so as to be communicated with the lead-in path part and which has an opening in a lap top face; and a recess portion which is provided in the end plate of the stationary scroll and which is intermittently communicated with the opening of the in-lap oil feed path pan.
 7. The rotary compressor according to claim 1, wherein the refrigerant contains at least one of tetrafluoropropene or trifluoropropene, which is a kind of hydrofluoroolefin, and the refrigerant has a global warming, potential within a range of 5 to 750, desirably 5 to
 350. 8. The rotary compressor according to claim 1, wherein the refrigerant contains, as a principal ingredient, tetrafluoropropene or trifluoropropene, which is a kind of hydrofluoroolefin, and difluoromethane and pentafluoroethane are mixed in the refrigerant so that its global warn potential falls within a range of 5 to 750, desirably 5 to
 350. 9. The rotary compressor according to claim 1, wherein the refrigerating machine oil is (1) polyoxyalkylene glycol, (2) polyvinyl ether, (3) poly(oxy)alkylene glycol or copolymer of its monoether and polyvinyl ether, (4) synthetic oil containing an oxygenated compound of polyol esters and polycarbonates, (5) synthetic oil containing alkylbenzenes as a principal ingredient, or (6) synthetic oil containing α-olefins as a principal ingredient. 